Retinoic acid receptor-related orphan receptors (RORs) are a subfamily of transcription factors in the steroid hormone nuclear receptor superfamily (Jetten & Joo (2006) Adv. Dev. Biol. 2006, 16, 313-355). The ROR family consists of ROR alpha (RORα), ROR beta (RORβ) and ROR gamma (RORγ), each encoded by a separate gene (in human: RORA, RORB and RORC, respectively; in mouse: rora, rorb and rorc, respectively). RORs contain four principal domains shared by the majority of nuclear receptors: an N-terminal domain, a highly conserved DNA-binding domain (DBD) consisting of two zinc finger motifs, a hinge domain, and a ligand binding domain (LBD). Each ROR gene generates several isoforms, differing only in their N-terminal domains. RORγ has two isoforms: RORγ1 and RORγ2 (also known as RORγt). RORγ refers to RORγ1 and/or RORγt. RORγ1 is expressed in a variety of tissues including thymus, muscle, kidney and liver, but RORγt is exclusively expressed in the cells of the immune system, has a critical role in thymopoiesis and the development of several secondary lymphoid tissues, and is a key regulator of Th17 cell differentiation (Jetten, 2009, Nucl. Recept. Signal., 7:e003, doi:10.1621/nrs.07003, Epub 2009 Apr. 3).
Th17 cells are a subset of T helper cells which preferentially produce the pro-inflammatory cytokines IL-17A, IL-17F, IL-21 and IL-22. Th17 cells and their effector molecules, such as IL-17, IL-21, IL-22, GM-CSF and CCL20, are associated with the pathogenesis of several autoimmune and inflammatory diseases, such as rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, psoriasis, inflammatory bowel disease, allergy and asthma (Maddur et al., 2012, Am. J. Pathol., 181:8-18). Recent findings support a role for IL17 and Th17 cells in the pathogenesis of acne (Thiboutot et al., 2014, J. Invest. Dermatol., 134(2):307-10, doi: 10.1038/jid.2013.400; Agak et al., 2014, J. Invest. Dermatol., 134(2):366-73, doi: 10.1038/jid.2013.334, Epub 2013 Aug. 7). Th17 cells are also potent inducers of inflammation associated with endometriosis, a chronic inflammatory disease (Hirata et al., 2010, Endocrinol., 151:5468-5476; Hirata et al., 2011, Fertil Steril., July; 96(1):113-7, doi: 10.1016/j.fertnstert.2011.04.060, Epub 2011 May 20). Additionally, Th17 cells have a key role in the mouse autoimmune models of experimental autoimmune encephalomyelitis (EAE), collagen-induced arthritis (CIA) and adjuvant-induced arthritis (AIA) (Bedoya et al., 2013, Clin. Dev. Immunol., 2013: 986789. Epub 2013 Dec. 26. Th17 cells are activated during inflammatory and autoimmune disease processes and are responsible for recruiting other inflammatory cell types, particularly neutrophils, to mediate pathology in target tissues (Miossec & Kolls, 2012, Nature Rev., 11:763-776; Korn et al., 2009, Annu. Rev. Immunol., 27:485-517). Aberrant Th17 cell function has been implicated in a variety of autoimmune diseases, including multiple sclerosis and rheumatoid arthritis. Autoimmune disease is believed to arise from the disruption of the equilibrium between effector and regulatory T cells (Solt et al., 2012, ACS Chem. Biol., 7:1515-1519, Epub 2012 Jul. 9). The importance of RORγt to Th17 cell differentiation and the pathogenic role of Th17 cells is evidenced by the fact that RORγt-deficient mice have very few Th17 cells and have a reduction in severity of EAE (Ivanov et al., 2006, Cell, 126:1121-1133).
Circadian rhythms are daily cycles of behavioral and physiological changes that are regulated by endogenous circadian clocks. A number of studies have established links between nuclear receptor (including RORγ) function and expression, the circadian regulatory circuitry, and the regulation of various physiological processes (Jetten (2009) op. cit.).
Obstructive sleep apnea syndrome (OSAS) is a chronic inflammatory disease regulated by T lymphocytes. OSAS patients have a significant increase in peripheral Th17 cell frequency, IL-17 and RORγt levels (Ye et al., 2012, Mediators Inflamm., 815308, doi: 10.1155/2012/815308, Epub 2012 Dec. 31).
A number of studies have provided evidence of a role of RORs in cancer. Mice deficient in the expression of RORγ exhibit a high incidence of thymic lymphomas that metastasize frequently to liver and spleen. High expression of Th17-associated genes (including RORγ) and high levels of Th17 cells in the tumor microenvironment has been shown to correlate with a poor prognosis in various cancers, including lung, gastric, breast and colon cancer (Tosolini et al., 2011, Cancer Res., 71:1263-1271, doi: 10.1158/0008-5472.CAN-10-2907, Epub 2011 Feb. 8; Su et al., 2014, Immunol. Res., 58:118-124, doi: 10.1007/s12026-013-8483-y, Epub 2014 Jan. 9; Carmi et al., 2011, J. Immunol., 186:3462-3471, doi: 10.4049/jimmunol.1002901, Epub 2011 Feb. 7; Chen et al., 2013, Histopathology, 63:225-233, doi: 10.1111/his.12156, Epub 2013 Jun. 6).
RORγ has also been identified to have a regulatory role in lipid/glucose homeostasis, and has been implicated in metabolic syndrome, obesity (Meissburger et al., 2011, EMBO Mol. Med., 3:637-651), hepatosteatosis, insulin resistance and diabetes.
Further support for the role of RORγ in the pathogenesis of inflammatory, metabolic, circadian effect, cancer, and autoimmune diseases and disorders can be found in the following references: Chang et al., 2012, J. Exp. Pharmacol., 4:141-148; Jetten et al., 2013, Frontiers Endocrinol., 4:1-8; Huh & Littman, 2012, Eur. J. Immunol., 42:2232-2237; Martinez et al., 2008, Ann. N.Y. Acad. Sci., 1143:188-211; Pantelyushin et al., 2012, J. Clin. Invest., 122:2252-2256; Jetten & Ueda, 2002, Cell Death Differen., 9:1167-1171; Solt et al., 2010, Curr. Opin. Lipidol., 21:204-211.
In light of the role that RORγ plays in disease pathogenesis, inhibition of RORγ activity and Th17 cell differentiation and activity, including IL17 production, will be of significant therapeutic benefit. It is therefore desirable to prepare compounds that inhibit RORγ activity and hence have utility in the treatment of inflammatory, autoimmune, metabolic, circadian effect, cancer, and other diseases mediated by RORγ, such as e.g., asthma, atopic dermatitis, acne, Crohn's disease, regional enteritis, ulcerative colitis, Sjögren's syndrome, uveitis, Behçet's disease, dermatomyositis, multiple sclerosis, ankylosing spondylitis, systemic lupus erythematosus, scleroderma, psoriasis, psoriatic arthritis, steroid resistant asthma and rheumatoid arthritis.